In December 2019, a cluster of pneumonia cases of unknown cause was linked to a seafood wholesale market in Wuhan, China. Unbiased sequencing identified a novel betacoronavirus, named 2019-nCoV, which formed a distinct clade within the sarbecovirus subgenus of the Orthocoronavirinae subfamily. The virus was isolated from human airway epithelial cells and detected in bronchoalveolar-lavage fluid samples from three patients. The 2019-nCoV genome was sequenced using Illumina and nanopore sequencing, and phylogenetic analysis revealed it to be distinct from SARS-CoV and MERS-CoV. The virus caused severe pneumonia in two of the three patients, one of whom died. The study highlights the importance of molecular techniques and unbiased sequencing in identifying novel pathogens and emphasizes the need for further investigation to understand the transmission and clinical impact of 2019-nCoV.In December 2019, a cluster of pneumonia cases of unknown cause was linked to a seafood wholesale market in Wuhan, China. Unbiased sequencing identified a novel betacoronavirus, named 2019-nCoV, which formed a distinct clade within the sarbecovirus subgenus of the Orthocoronavirinae subfamily. The virus was isolated from human airway epithelial cells and detected in bronchoalveolar-lavage fluid samples from three patients. The 2019-nCoV genome was sequenced using Illumina and nanopore sequencing, and phylogenetic analysis revealed it to be distinct from SARS-CoV and MERS-CoV. The virus caused severe pneumonia in two of the three patients, one of whom died. The study highlights the importance of molecular techniques and unbiased sequencing in identifying novel pathogens and emphasizes the need for further investigation to understand the transmission and clinical impact of 2019-nCoV.